Secrecy system for extension and party-line telephones.



C. C. BRADBURY.

SECRECY SYSTEM FOR EXTENSION AND EARTY LINE TEL'EPHONES.

' APPLICATION FILED 1AN.21.1915.

1521,1840 Patented Apr. 3,1917.

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CLIFFORD G. BRAIDBURY, 0F MOUNT VERNON, NEW YORK, ASSIGNOR, BY IVIESNE ASSIGN- MENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION 0]? new YORK.

Specification of Letters Patent.

Patented Apr. 3, 1917.

Application filed January 27, 1915. Serial No. 4,641.

To all whom it may concern:

Be it known that I, CLIFFORD C. BRAD- BURY, a citizen of the United States, residing at Mount Vernon, in the county of Vestchester and State of New York, have inrented certain new and useful Improvements in Secrecy Systems for Extension and Party-Line Telephones, 01'' which the following is a full, clear, concise, and exact description.

This invention relates to secrecy systems for extension and party line telephones and more particularly it relates to a system in which a plurality of subscribers stations are associated with a single telephone line in an arrangement such that the subscriber at each station may employ the line without endangering the secrecy of his conversation.

The object of this invention is to provide a simple yet effective means whereby a subscriber using any station of such a party line group may at will isolate the other stations from the line.

In my invention each station is provided with a switch for discontinuing the extension of one or both line conductors beyond that station, the arrangement of the stations being such that one of the two exchange line conductors is carried first to one of the stations extended through switch con tacts at that station to the next station in order and similarly extended consecutively to each of the other stations of the party line group. The other of the two line conductors is similarly extended to each of the stations but in. the reverse order. With this arrangcinent it is possible, by operating the switch at a given station, to prevent the stations on either side of that station from gaining access to the line.

The arrangement is one which is applicable for example to a case where a number of telephones in a single business office or suite of oiiices are connected to a single exchange line and where, as often happens, a person using one of these telephones wishes to assure himself that others in the oflice cannot overhear his conversation.

This invention will be more clearly understood by reference to the accompanying drawing which shows four subscribers stations 1, 5, 6 and 7 arranged for connection with a pair of exchange line conductors 8 and 9. Line conductor 8 is extended first to station a, thence through contact 10 of key 11 associated with station 1 to station 5, thence through contact 12 of key 13 associated with station 5 to station 6, thence through contact 14 of key 15 associated with station 6 to station 7. Conductor 9 is similarly carried to the different stations but in reverse order, namely, first to station 7, thence through contact 16 of key 17 asso' ciated with station 7 to station 6, thence through contact 18 of key 15 to station 5, thence through contact 19 of key 18 to station 4;.

Each of the stations, for example station 5, may be equipped with the customary transmitter 25, receiver 26, induction coil 27, condenser 28, ringer 29, and switch hook 30. The removal of receiver 26 from the switch hook 3O closes the talking circuit of station 5 in the customary manner and when keys 11, 13 and 17 are in their normal or closed position, places this station in circuit with the line conductors 8 and 9 and the central oilice battery 31. If new the receiver of any of the other stations 4, 6 or 7 is removed from its hook, that station will be placed in parallel with station 5 and in conversational relation with line conductors 8 and 9, provided key 13 is in its normal closed position. When key 13 is operated contacts 12 and 19 will be opened. The opening of contact 12 breaks the connection between the conductor 8 and stations 6 and 7 and similarly the opening of contact 19 breaks the connection between conductor 9 and sta- 17101141.

Thus the person using the station 5 may at will, by operating key 13 make it impossible for stations 1, 6 and 7 to gain access to the exchange line 89. The circuit of station 5 is not, however, affected by the operation of key 13, such circuit being maintained from the central office battery 31 by way of conductor 8, contact 10 of key 11, winding 32 of induction coil 27, switch hook 30, transmitter 25, contact 18 of key 15, contact 16 of key 17 and conductor 9 back to battery.

In a like manner any of the other stations 4, 6 or 7 may at will, be placed in sole conyersational connection with the exchange line by the operation of the keys 11, 15 or 17 respectively, which is associated with that particular station.

While the system herein depicted contains only four stations, it is to be understood that the system can be extended or contracted to include'a greater or less number of stations as desired. If only two stations were desired, the arrangement of stations 4 and 7 would doubtless be employed, whereas a greater number of stations would require a multiplication of the stations of the type of station 5. V

, Furthermore, while the invention has been shown as applied to a common battery system, it is equally adaptable to a local battery party line system, inasmuch as the secrecy feature is obtained by manual means and without the use of relays or other electromagnetic devices.

What is claimed is:

1. In a telephone system, line conductors, a plurality ofsubscribers stations normally connectible thereto, and a key individual to each of said stations'whereby the other stations may at will be isolated from said line conductors without interrupting the connection of the station individual to said key with said line conductors.

2. In a telephone system, line conductors,

v a plurality of subscribers stations said stations being normally connectible individually or collectively to said line conductors, and a key at each of said stations for rendering said station alone connectible to said 1 line conductors. r

' 3. In a telephone system, line conductors, a plurality of subscribers stations consecutively arranged, switch contacts at each of said stations and within the control of the subscriber at said station, each station being connectible to one of said line conductors through switch contacts controlled at the preceding station, and connectible to the other of said line conductors through switch contacts controlled at the succeeding station.

4:. In a telephone system, a plurality of subscribers stations, a dentral oflice and a pair of line conductors extending therefrom to said stations, one oi' said line conductors extending from the central oflice through said stations in one direction and the other extending from the central oflice through said stations in the opposite direction, a pair of normally closed switch contacts in each line conductor and individual to each station excepting the end stations, the subscribers circuit at each of said stations other than the end stations being bridged from a point in one line conductor on the central office side of its normally closed contacts in that conductor to a point in the other conductor on the central oflice side of its normally closed contacts in that conductor, whereby the subscribers circuit at that station will remain in bridge of the telephone line, and one of the limbs of the telephone line will be interrupted between the central office and all of the stations on one side of the bridged station and the other limb of the telephone line will be interrupted between the central oflice and all of the stations on the other side of the bridged station when the two sets of contacts for one station are interrupted.

In witness whereof, I hereuntov subscribe my name this 14th day of January A. 1)., 1915.

CLIFFORD C. BRADBURY.

Witnesses:

E. EDLER, K. L. STAHL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, 1 Washington, D. C. 

